The present invention relates to a line start reluctance synchronous motor, and more particularly, to a line start reluctance synchronous motor in which a magnet unit is free-rotatably installed between a stator and a cage rotor and the magnet unit and the cage rotor are synchronously operated.

A single phase line start permanent magnet synchronous motor which is started by interaction between the magnetic field of a coil and of a secondary conductor is known (EP 1 267475 A2).

As shown in Figs. 1 and 2, the conventional induction motor comprises a motor body 1 serving as a casing, a stator 2 arranged along an inner circumferential surface of the motor body 1, and an AC squirrel cage rotor 3 rotatably arranged based on a rotation shaft 4 at the center of the stator 2.

The stator 2 is formed as lamination structure of a plurality of silicon steel sheets, and is provided with a plurality of coil winding teeth 5 therein. A plurality of slots 6 are formed between the coil winding teeth 5 with a certain interval, and coil 7 is wound on the coil winding teeth 5 through the slots 6.

The rotor 3 is formed of a lamination structure of a plurality of silicon steel sheets, a rotor bar hole 9 is formed at the laminated sheet with a certain interval, and a rotor bar 10 of aluminum is inserted into the rotor bar hole 9. An end ring 11 is connected to both ends, upper and lower portions of the rotor bar 10.

Operation of the conventional induction motor will be explained as follows. When a power source is applied to the coil 7, a rotating magnetic field is generated by a current which flows in the coil 7 and an induction current is generated at the rotor bar 10.
By an interaction between the generated rotating magnetic field and the induction current, a rotation torque is generated at the rotor 3 and the rotation torque is outputted through the rotation shaft 4.

However, in the conventional induction motor, a current for generating the rotating magnetic field and an induction current generated from the rotor are supplied through coil connected to an external power source. Due to this first loss generated from coil of the stator and a second loss generated from the rotor bar of the rotor, an excessively current loss is generated thus lowering the efficiency, of the motor. Furthermore, additional noise is created.

Therefore, the object of the present invention is to provide a line start reluctance synchronous motor capable of lowering noise and enhancing its efficiency.

This object is solved in accordance with the present invention by a line start reluctance synchronous motor comprising the features of claim 1.

Improvements of this motor and further features thereof are subject of the claims dependent from claim 1.

The present invention resides in free-rotatably arranging a magnet unit between a stator and a cage rotor, by uniformly forming pole numbers of the stator, the magnet unit, and the cage rotor, and thus by synchronously operating the magnet unit and the cage rotor.

In accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a line start reluctance synchronous motor comprising: a single phase stator arranged at an inner circumferential surface of a motor body and on which a main coil and a sub coil are wound; a magnet unit free-rotatably arranged along an inner circumferential surface of the stator in order to maintain an air gap with the stator; and a cage rotor provided with a rotation shaft at a center portion thereof to be rotatable along an inner circumferential surface of the magnet unit, provided with a cage bar at a peripheral portion thereof, and provided with magnetic barriers having the same pole numbers as the magnet unit.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

Fig. 1:

is a longitudinal section view showing an induction motor in accordance with the conventional art;

Fig. 2:

is a section view taken along line II-II of Fig. 1;

Fig. 3:

is a longitudinal section view showing a line start reluctance synchronous motor according to the present invention;

Fig. 4:

is a sectional view taken along line IV-IV of Fig.3;

Fig. 5:

is a view showing an extracted main part of Fig.4;

Fig. 6:

is a graph showing a synchronous operation of a magnet unit and a cage rotor for a torque and rpm;

Fig. 7:

is a graph showing a synchronous operation of the magnet unit and the cage rotor for operation time and rpm;

Fig. 8:

is a longitudinal section view showing another embodiment of the cage rotor in the line start reluctance synchronous motor according to the present invention; and

Fig. 9:

is a longitudinal section view showing still another embodiment of the cage rotor in the line start reluctance synchronous motor according to the present invention.

As shown in Figs. 3 to 5, a line start reluctance synchronous motor according to the present invention comprises: a single phase stator 110 arranged at an inner circumferential surface of a motor body 101 and on which a main coil 113 and a sub coil 114 are wound; a magnet unit 120 free-rotatably arranged along an inner circumferential surface of the stator 110; and a cage rotor 130 provided with a rotation shaft 102 at a center portion thereof to be rotatable along an inner circumferential surface of the magnet unit 120, provided with a cage bar 115 at a peripheral portion thereof, and provided with magnetic barriers 201 and 202 having the same pole numbers as the magnet unit 120.

The stator 110, the magnet unit 120, and the cage rotor 130 are arranged to always maintain constant intervals G1 and G2.

A rotation shaft bearing 103 is arranged between the rotation shaft 102 and the motor body 101 thus to prevent the rotation shaft 102 from being influenced by the motor body 101.

The stator 110 is formed of a lamination structure of a plurality of silicon steel sheets, and is provided with a plurality of coil winding teeth 111 therein. A plurality of slots 112 are formed between the coil winding teeth 111 with a certain interval, and the main coil 113 and the sub coil 114 are wound on the coil winding teeth 111 through the slots 112.

The magnet unit 120 free-rotatably arranged between the stator 110 and the cage rotor 130 by a rotating magnetic field is constructed as follows:

First, a cylindrical ring magnet 121 is arranged between the stator 110 and the cage rotor 130, and a non-magnetic substance of a cup shape, a supporter 122 is coupled to one end of the ring magnet 121. Also, a bearing 123 is forcibly inserted into a center of the supporter 122 to be rotatably coupled to an outer circumferential surface of the rotation shaft 102.

The cage rotor 130 is formed of a lamination structure of a plurality of silicon steel sheets, and is provided with a salient 203 having the same pole numbers as the magnet unit 120 at an outer circumferential surface thereof.

A plurality of magnetic barriers 201, 202 are formed at the rest surface of the cage rotor 130 excluding the cage bar 115.

The magnetic barriers 203 are formed as a circular arc shape between the rotation shaft 102 and the salient 131, and an air space portion 133 is formed between each salient 131.

The magnetic barriers 203 gradually become large towards a circumferential direction of the cage rotor 130 on the basis of the rotation shaft 102, and three pairs of magnetic barriers 203 are arranged on the basis of each d axis.

A plurality of cage bar holes 116 are formed with a certain interval at a peripheral portion of the cage rotor 130, and the cage bar 115 of Al or Cu is inserted into the cage bar hole 116 by a die casting method. Also, an end ring 117 is connected to both ends, upper and lower portions of the cage bar 115.

Hereinafter, operation of the line start reluctance synchronous motor according to the present invention will be explained as follows.

When a power source is applied to the main coil 113, the magnet unit 120 is freely rotated by a current which flows in the main coil 113.

At this time, the supporter 122 is freely rotated on the basis of the rotation shaft 102 by the bearing 123 thereof, and the magnet unit 120 is freely rotated since the ring magnet 121 is coupled to the supporter 120.

The magnet unit 120 is rotated and at the same time, generated a rotating magnetic field of a strong magnetic flux, thereby rotating the cage rotor 130.

That is, by the rotating magnetic field of the stator 110, the magnet unit 120 of a low inertia state is operated, rotated, and synchronized. At the same time, the magnetic unit 120 generates a rotating magnetic field and supplies a torque generating magnetic flux to the cage rotor 130, thereby rotating the cage rotor 130.

At this time, since the magnet unit 120 has the same pole numbers as the cage rotor 130, the cage rotor 130 is operated with a synchronous speed with the magnet unit 120 without a slip.

As aforementioned, the synchronous speed can be expressed as 120*F/P (herein, F denotes a power source frequency (Hz), and P denotes pole numbers). When the power source frequency is supposed to be constant, the synchronous speed is determined by the pole numbers. Accordingly, since the pole numbers of the stator 110, the pole numbers of the magnet unit 120, and the pole numbers of the cage rotor 130 are the same one another, the magnet unit 120 is synchronized with the stator 110 and the cage rotor 130 is synchronized with the magnet unit 120.

In Fig. 6 a thin solid line shows the cage rotor, a dotted line shows a load of the rotation shaft, and a thick solid line shows a synchronous operation of the magnet unit and the cage rotor.

Referring to Fig. 6, when the cage rotor and rpm of the rotation shaft reach a synchronization speed point 'a', the number of rotation is always maintained constantly on the vertical line of the 'a' point regardless of a load thereby to perform a synchronization operation.

In Fig. 7 a thin solid line shows the cage rotor and a thick solid line shows the magnet unit.

Referring to Fig. 7, up to an initial time b, rpm of the cage rotor and rpm of the magnet unit are different each other thus to generate a slip. However, after a certain time point 'c', the rpm of the cage rotor becomes the same as the rpm of the magnet unit.

That is, the cage rotor and the magnet unit are synchronously operated by being rotated with the same synchronous speed thus not to generate a slip. According to this, a second current loss is not generated and thereby a low noise operation and a high efficiency operation are possible.

In Fig. 8 a plurality of inner magnetic barriers 301 are formed as a circular arc shape at an inner side of a cage rotor 330. The inner magnetic barriers 301 have the same pole numbers as a magnetic unit 320.

In Fig. 9 a plurality of outer magnetic barriers 402 are formed at an outer circumferential surface of a cage rotor 430. A salient 403 is formed between the outer magnetic barriers 402.

As aforementioned, according to the present invention, the magnet unit is free-rotatably installed between the stator and the cage rotor, and the pole numbers of the stator, the pole numbers of the magnet unit, and the pole numbers of the cage rotor are the same one another thus to synchronously operate the magnet unit and the cage rotor, thereby enabling a low noise operation and a high efficiency operation with a low cost.